The present invention relates to a gasoline dispensing system and method and, more particularly, to such a system and method in which the flow rates of the fluid are selectively measured.
In fluid flow systems, such as gasoline services station installations, the gasoline is pumped from an underground storage tank, through a conduit, or tube, to a dispenser unit, and through a hose extending from the dispenser unit to a nozzle for dispensing the gasoline into a vehicle tank. A system valve is provided to control the gasoline flow, and a meter is connected in the system for metering the flow so that the volume of gasoline dispensed can be displayed on the dispenser unit and the customer charged accordingly. Ideally, during nonuse of the dispensing nozzle, gasoline will remain in the conduit between the storage tank and the dispensing unit and in the hose extending from the dispensing unit to the nozzle until the system valve and pump are turned on to pressurize the hose and permit the discharge of the gasoline through the nozzle. However, long periods of inaction, volumetric changes in the fuel due to temperature changes, and imperfect check valves in the system can cause some of the fluid in the conduit and the hose to leak back into the storage tank during non-use. Thus, when this happens and the pump is turned on and the valve is opened preparatory to dispensing the gasoline into a vehicle, a small volume of fuel will flow through the meter until the conduit and the hose are fully pressurized. Unfortunately, this volume of this fuel is often large enough to be metered and therefore displayed on the dispenser volume display. Since the dispensing nozzles are designed not to dispense gasoline when the pressure is below a certain limit, the meter will cause the register to display a dispensed volume of gasoline, even though no gasoline has actually been dispensed from the nozzle. This, of course, causes the customer to be charged for gasoline that is not actually dispensed.
Therefore, what is needed is a gasoline dispensing system and method that does not meter of display the flow of any gasoline in the system when none is being dispensed to the customer.